Lack of inter-muscular coherence of axial muscles in Pisa syndrome Abstract Background Pisa syndrome is a lateral deviation of the trunk described in Parkinson’s disease (PD). Its etiology is still unknown; advanced muscular signal analysis techniques, such as inter-muscular coherence, could help clarifying its pathophysiology and suggest therapeutic strategies. Methods Fourteen idiopathic PD subjects with a lateral deviation of the trunk of at least 10° were included. Electromyographic (EMG) signal was recorded from bilateral thoracic, and lumbar para-spinal and obliqui externi muscles. The synchronization between EMG right and left side signals was quantified using the magnitude-squared coherence function. Results In our sample, coherence (range 0–1) did not exceed 0.3, which indicates a lack of intra-muscular coherence. Conclusion This finding is suggestive of a defective muscular fine-tuning, which has been associated with bradykinesia. These data support the hypothesis of PS as a clinical sign of bradykinesia, impacting on therapeutic and rehabilitative options.